Transformer insulation.



W. M. MCCONAHEY.

TRANSFORMER INSULATION.

APPLICATION FILED JAN. 30, I914.

9 Patented May 1, 1917.

v I INVENTOR UNITED STATES PATENT OFFICE.

WILLIAM M. MCCONAHEY, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

TRANSFORMER INSULATION.

Specification of Letters Patent.

Patented May 1, 1917.

Application filed January 30, 1914. Serial No. 815,330.

and low-tension windings are composed of concentric coils which are embraced by a plurality of iron cores that provide circuits for the magnetic flux. In order to provide a transformer of high operating efiiciency, it is important that the amount of space occupied by the insulation applied to the windings shall be minimized in order to improve the space-factor of'the transformer. To insure the high-tension winding of the transformer against grounding through the iron core, it is convenient to dispose the high tension coil between two sections of lowtension winding and to interpose adequate insulating. means where the high-tenslon winding is in proximity to the iron cores. This arrangement minimizes the quantity of insulating material required, and, consequently, precludes low operating efliclency and poor regulation of the transformer which result from a poor space-factor.

For a better understanding of my invention, reference may be had to the following description and the accompanying drawing in which Figure 1 is a plan view, partially in section, of a transformer embodying a form of my invention; Fig. 2 is a view of a portion of the transformer in transverse section, taken along the line AB, ofFig. 1; Fig. 3 is a perspective view of a hightension transformer coil constructed in accordance with my invention, and Fig. 4. is an enlarged sectional view of a portlon of the coil shown in Fig. 3.

The transformer comprises a high-tension winding 1 interposed between coil sections 2 and 3 of the low-tension winding, the said windings comprising concentrically disposed coils substantially as shown in Fig. 1. Core members 4, 5, 6 and 7 embrace the high and low-tension coils and provide paths of low reluctance for the magnetic flux gener- 5 ated by current traversing the transformer windings. The core members 6 and 7 are s1m1lar, as are the core members 4 and 5.

Inasmuch as it is desirable'that the mean turn of the transformer windings shall be as short as is consistent with satisfactoryoperation, the portions of the core members that are disposed within the opening 8 are worked at higher magnetic densities than the portions of the cores that are external thereto. As the voltage usually impressed upon the high-tension winding 1 is suflicient to disrupt ordinary insulation interposed between said Winding and the core members, I provide some of the coils comprising the hi gh-tension winding 1 with insulating chain nel pieces 9 to preclude the grounding of said winding through the core members.

In Fig. 2, the arrangement of the transformer coils and core members is more clearly set forth. To improve the insulating properties and for convenience in winding and assembling, the high-tension winding 1 is divided into a plurality of coils 10, 10*, etc., which are superposed, one above the other, and suitably bound togetherby means of tape. The low tension coil sections! and 3 are wound in the form of substantially long tubular members and of such dimensions as to permit of the interposition of the .85

coils 10, 10, etc. The low-tension coil sections 2 and 3 are adequately insulated from the high-tension winding 1 and the core members'by suitable insulating fabric. It will be seen that the core members are adjacent to the high-tension. winding 1 only where the insulating channel pieces 9 are interposed at the outer surfaces of the top and bottom coils of the high-tension winding, as shown on coil 10 of Fig. 3. The insulating channel pieces 9 are preferably made of micarta which possesses a high dielectric strength and withstands severe stresses and hi h temperatures without impairing its insiilating properties.

Inasmuch as the core members 56 and 7 are spaced apart, it is unnecessary to provide channel pieces 9 which extendthe entire periphery of the high-tension winding 1. It is suflicient that the said channel pieces be applied only where the core members are in close proximity to the high-tension coils. In Fig. 3, the channel pieces 9 are shown as applied to only those portions ofthe coil 10 which are in close physical contact with the core members. Upturned' edges 11 formed upon the channel pieces 9 provide a leakage path of substantially high resistance to preclude the creeping of the high-tension current in the coil 10 to the core members.

I prefer that the high-tension coils, which are to be equipped with the channel pieces 9, shall be wound substantially as indicated in Fig. 4:. The layers that are wound with conductors 12, and are received by the channel piece 9, comprise fewer turns than the other layers of the coil. This arrangement permits the channel pieces 9 to be applied without causing objectionable open spaces to intervene between the low-tension coils 2 and 3 which would result if the channel pieces 9 were allowed to project beyond the outer surface of the coil.

From the above description, it will be apparent that, by the utilization of my invention in transformer construction, the quantity of insulating material may be considerably reduced from that required in transformers as heretofore constructed. At the same time, no sacrifice is made in the ability of the insulation to withstand the high-potential stresses to which the transformer may be subjected; My invention also improves the space factor of the transformer which results in high operating efliciency and better regulation of the terminal voltage.

I claim as my invention:

1. A transformer comprising high tension coils, inner and outer low tension coils coextensive therewith, core members embracing the coils, insulating channel pieces interposed between the adjacent surfaces of said core members and the high tension coils, the outer conductor layers of the high tension coils being inclosed by the channel pieces and the other conductor layers comprising a greater number of convolutions than said outer conductor layers.

2. A transformer comprising concentrically-disposed coils, the high tension coils being interposed between the low tension coils that are co-extensive therewith, a plurality of magnetizable core members embracing the coils, and insulating channel pieces interposed between adjacent surfaces of the high tension coils and the magnetizable core members, said channel pieces receiving a plurality of convolutions of the coil, and other convolutions thereof being superposed by the upturned edges of said channel pieces in order to improve the space factor of the trans-4 former.

3. A current-carrying coil comprising a plurality of superposed conductor layers having a multiplicity of convolutions, and an insulatin channel piece applied to an exposed surface of the coil and receiving some of said conductor layers, the conductor layers not inclosed by said channel piece comprising the greater number of convolutions per layer and extending to the outer surfaces of the upturned edges of said channel piece.

-l. A current-carrying coil comprising a plurality of superposed conductor layers having a multiplicity of convolutions, and an insulating channel piece receiving some of said conductor layers, the remainin conductor layers extending to the outer edges of said channel piece in order to form a smoothsurfaced coil side.

5. A current-carrying coil comprising superposed conductor layers having a plurality of convolutions of a uniform conductor, and an insulating channel piece receiving some of said conductor layers, the remaining conductor layers not inclosed by said channel piece comprising convolutions that extend to the outer surfaces of the upturned edgesof said channel piece.

In testimony whereof, I have hereunto subscribed my name this 23rd day of Jan, 1914.

WILLIAM M. MGCONAHEY.

\Vitnesses LENORE FLANAGAN, B. B. HINES. 

